SiC PVT Crystal Growth with Flat Isotherms for Large Diameters
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Solution Overview
Problem
The high cost and quality issues of SiC substrates, particularly due to crystal defects and stress/strain, hinder the widespread application of SiC-based and GaN-based devices, while existing PVT growth methods struggle to achieve flat growth interfaces and uniform temperature gradients for large-diameter SiC crystals.
Innovation Solution
A PVT growth apparatus with a flat resistive heater positioned below the crucible and tailored thermal insulation inserts creates axial heat fluxes, resulting in flat isotherms and reduced radial temperature gradients, producing high-quality large-diameter SiC single crystals with minimal defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional PVT growth methods are used, then SiC single crystals can be grown, but radial temperature gradients and curved growth interfaces are formed leading to crystal defects
Solution Approach 1:
The heating system is divided into multiple independent heating zones along the crucible height, allowing separate control of temperature in different regions. This segmentation enables precise control of the radial temperature gradient to achieve a flat growth interface while maintaining overall growth process stability.
Solution Approach 2:
The patent changes the temperature distribution parameters by implementing non-uniform heating across different crucible zones. By adjusting the power distribution to individual heating zones, the radial temperature gradient is optimized to eliminate curved growth interfaces and associated crystal defects.
2Productivity
If large-diameter SiC substrates are produced, then device cost is reduced, but crystal defects such as threading dislocations and basal plane dislocations increase
Solution Approach 1:
The crucible is divided into multiple heating zones with independent temperature control, allowing each zone to be optimized for specific growth requirements. This enables stable growth of large-diameter crystals by preventing thermal instabilities that would otherwise cause dislocations and other defects.
Solution Approach 2:
Temperature sensors are positioned at multiple locations within the crucible to provide real-time feedback on the thermal field distribution. This feedback is used to dynamically adjust the heating power in each zone, maintaining optimal temperature gradients throughout the growth process and preventing defect formation in large-diameter substrates.
3Device complexity
If conventional heating arrangements are used, then heating is simple, but curved growth interfaces and stress in the crystal are generated
Solution Approach 1:
The heating system is segmented into multiple independent zones with individual heating elements or independently controllable heating sections. This allows the complex temperature distribution required for flat growth interfaces to be achieved through coordinated control of simpler, modular heating components.
Solution Approach 2:
The heating system transitions from a static, uniform heating arrangement to a dynamic, zone-controlled system. Each heating zone can independently adjust its power level in response to real-time temperature measurements, enabling the heating system to adapt and maintain optimal conditions for flat interface growth throughout the crystal growth process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method yields SiC substrates with improved crystal quality, reducing defects and stress, enabling cost-effective fabrication of large-diameter SiC and GaN-based devices with enhanced performance.
Implementation Method 1
crucible 1 is heated by heating means 4 to a temperature between 2000° C. and 2400° C. sufficient to vaporize the SiC source material 2
Implementation Method 2
Crucible 1 is surrounded by thermal insulation 5 inside of chamber 20
Implementation Method 3
Driven by this temperature gradient, the vapor species 7 migrate toward SiC seed 3, as illustrated schematically by arrow 7, and condense on SiC seed 3 causing growth of a SiC single crystal 6 on SiC seed 3
Data Source
AI summary
In an apparatus and method growing a SiC single crystal, a PVT growth apparatus is provided with a single crystal SiC seed and a SiC source material positioned in spaced relation in a growth crucible. A resistance heater heats the growth crucible such that the SiC source material sublimates and is transported via a temperature gradient that forms in the growth crucible in response to the heater heating the growth crucible to the single crystal SiC seed where the sublimated SiC source material condenses forming a growing SiC single crystal. Purely axial heat fluxes passing through the bottom and the top of the growth crucible form a flat isotherm at least at a growth interface of the growing SiC single crystal on the single crystal SiC seed.